Methods and apparatus for unidirectional timing message transport over packet networks

Abstract

Methods and apparatus for synchronizing a first clock of a transmit node and a second clock of receive node in a packet network are provided. Consecutive intervals of time-stamped packets transferred from the transmit node to the receive node are selected. The consecutive intervals have a difference in delay noise within a defined acceptance window. A correction factor is determined for the second clock in accordance with transmit and receive time stamps of transferred time-stamped packets bounding the consecutive intervals. The correction factor is applied to the second clock to synchronize the second clock of the receive node with the first clock of the transmit node.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to packet transfer networks and, more particularly, to timing information transmission over packet networks.BACKGROUND OF THE INVENTION[0002]In order to synchronize clock sources on both ends of a packet transfer network, timing information is transmitted between a clock source of a transmit node and a clock source of a receive node. However, standard time synchronization protocols can be inaccurate and typically result in long synchronization times. Further, such protocols have very poor tolerance for the uncertain and varying delay of synchronization signals from the transmit node to the receive node of the packet transfer network, commonly known as packet delay variation (PDV).[0003]One such example of an existing time synchronization protocol is the Standard Precision Time Protocol (PTP) IEEE 1588. IEEE 1588 utilizes two phases in a synchronization process. The first phase corrects the time difference between th...

AI Technical Summary

Benefits of technology

The present invention provides a method for synchronizing clocks in a packet network with high variation of propagation delay. This is achieved by selecting consecutive intervals of transferred time-stamped packets with a difference in delay noise within a defined acceptance window. A correction factor is determined for the second clock based on the transmit and receive time stamps of the consecutive intervals and applied to synchronize the second clock with the first clock. The method is fast and tolerates high PDV, providing better frequency synchronization.

Problems solved by technology

However, standard time synchronization protocols can be inaccurate and typically result in long synchronization times. Further, such protocols have very poor tolerance for the uncertain and varying delay of synchronization signals from the transmit node to the receive node of the packet transfer network, commonly known as packet delay variation (PDV).

However, IEEE 1588 is not capable of tolerating PDV at high orders of magnitude.

Further the bidirectional message transmittal is slower and less accurate in determining synchronization times.

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